The human digestive system is a complicated physiological entity which has the role of both breaking down consumed food and beverages as well as absorbing the nutrients from the food. The breaking down process involves several enzymes, which are special proteins that are used to break down larger molecules, such as carbohydrates, fats, and proteins into their simple sugars, lipids, and amino acids, which are more easily absorbed by the digestive system.
Mouth
The human digestive system begins in the mouth. The process of chewing breaks food up into smaller particles, a process which is helped by the moisturizing abilities of saliva. Saliva also has another component which aids the digestive process, amylase. Amylase is an enzyme that helps break starch down into sugar.
Esophagus
The next portion of the human digestive system is the esophagus. The esophagus works to connect the mouth and the stomach. The esophagus is able to move foods and liquids down into the stomach via the rhythmic contraction of smooth muscle outside of the esophagus. This procedure, called peristalsis, allows humans to drink even when they are upside-down.
Stomach
The human digestive system continues with the stomach. The stomach secretes gastric acid which helps break foods down. This acid also activates another enzyme, called pepsin, which begins to break proteins down into substances which can be absorbed by the intestine. The stomach also is responsible for mixing of the food with these gastric juices to produce a partially digested mixture called chyme.
Pancreas
The pancreas is the other major supplier of digestive enzymes within the human digestive system. The pancreas produces and secretes enzymes which break down fats, carbohydrates and proteins into smaller forms which can then be absorbed. The pancreas also secrets bicarbonate, a substance which neutralizes the acid from the stomach, preventing damage to the intestines.
Intestines
The intestines are the portion of the digestive system where the nutrients from the food are absorbed by the body. The intestines absorb the digested carbohydrates, lipids, and amino acids (from the proteins) as well as vital vitamins and nutrients. After the nutrients have been absorbed by the small intestine, water is absorbed by the large intestine, which also compacts the remaining waste into feces.
